Electronic circuit



Patented Feb. 1, 1949 UNITED STATE s PATENT oFFIcE ELECTRONIC omourrville, 111.

Application January 4, 1947, Serial No. 720,229

2 Claims.

1 This invention relates to a means for deionizing a gas-filled tubeonce it is ionized. It particularly relates to an electronic circuit inwhich a vacuum tube is connected inseries with a gas-filled tube,

rent potential thatonce it is i0nized,it will con- :1

tinue to ionize until the circuit is broken regardless of how negativein potential the control grid is driven. In the prior art, mechanicalswitches, time delay relays and other mechanical devices have been usedto interrupt the circuit. However,'

mechanical switches and the like, or anything involving mechanical meansfor interrupting the circuit, have the disadvantages that are inherentin all mechanical means. Mechanical means are never as instantaneous intheir reaction as electronic means. Mechanical means require more upkeepand if a switch sticks, the desired result is not obtained. There isnothing to go wrong with electronic means such as is described herein.Electronic means are instantaneous and will always respond in therequired manner.

Broadly my invention comprises connecting the gas-filled tube in serieswith a vacuum tube across a source of direct current potential. 'Theflow of currentthrough the vacuum tube is accomplished by the control ofa control grid in the vacuum tube. The control grid in the vacuum tubewill control the now of current through the circuit and if sufficientnegative potential is placed on the control grid in the vacuum tube, thevacuum I tube will cease to conduct and'in 'efiectbecomes an electroniccircuit breaker. The device will work equally well whether the vacuumtube is in the plate circuit of the gas-filled-tube or is in the cathodecircuit of the gas-filled tube.

It is therefore an object of this invention to provide an improvedmeans-for breaking the circuit of a gas-filled tube which has onceionized by employing a vacuum tube in series with a gasfilled tube.

Other advantages, objects and uses of my invention will become apparentbyreferring to the drawin s in which Figure 1 illustrates a circuit withthe vacuum tube in the anode circuit of the I as-filled tube.

- the resistor 20.

Figure 2 illustrates a' similar circuit with thevacuum tube in thecathode circuit of a gas-filled tube.

For sake of illustration the drawings are described in connection withphotoelectric inspection operation although my invention will applyequally well to any operation where the gasfilled tube is ionized byappropriate means and when it is desired-to deionize the tube, anegative potential is placed on the control grid in the vacuum tube.

Referring to Figure 1, a gas-filled tube I0 is pro vided having an anodecircuit II, a cathode circuit I2 and a control grid I3. Vacuum tube I4.is connected in the anode circuit I I in series with the'gas-filledtube Ill. The vacuum tube I 4 has a cathode circuit I5, an anode circuitI 6 and a control grid I1. The two tubes I0 and I4 are connected inseries across a direct current source of potential in which the positiveterminal of the direct current source is at I8 and is grounded at I9. Inthe particular illustration of Figure 1, the control grid I3 iscontrolled photoelectrically by the amount of light received by thephototube I9. The phototube I9 is connected in series with the resistor20 across a source of direct current potential having its positiveterminal at 2! and its negative terminal at 22. The control grid I3 isconnected at 23 between the phototube I9 and When the phototube It is inshadow, the control grid I3 is more negative than the cathode I2 and thegas-filled tube I!) will not conduct. However when the phototube I 9receives light, a positive potential is placed on the control grid I 3and if at the same time the positive potential is placed on the controlgrid I'l, current will flow through the circuit employing the tubes l0and I4. Once the tube I0 is ionized by such a condition, the controlgrid I3 will no longer be able to control the flow of current throughthe circuit although the tube I 9 is placed in darkness, because this isa characteristic of a gas-filled tube as has been heretofore explained.However, the flow of current through the circuit from the point I 8 tothe point I9 can be stopped if the potential on the ground grid I1 ischanged from positive to negative. In other words, the control grid I1is effective at any time for stopping the flow of current through thecircuit where as the control grid I3 can function only to initiate theflow but cannot stop the current once the tube III is ionized. Theparticular manner of controlling the control grid is immaterial to'myinvention. The control grid could be com nected'to a switch. which wouldalternate from a conduct.

positive potential to a negative potential. However in the illustrationgiven, the control grid ll is also controlled photoelectrically. This"is done as follows: r

A second vacuum tube 2% is provided having a control grid 25, an anodecircuit 25, and a cathode circuit 21. The tube E i is connected inseries with a load resistor 28 and a biasing resistor 29 across a directcurrent source of potential having its positive terminal at 3B and itsnegative terminal at 23%. The control grid ll of the. tube It isconnected to the point 32 between the resistor 28 and the tube 2 By sucha connection the tubes and 25 are 186 out of. phase; That is when tube24 is conducting, tube M is rendered non-conducting and when tube 25 isnon-conducting, tube I2 is conducting. The bias on the tube 25 iscontrolled by a photoelectric circuit employing the phototube 33connected in series with a resistor ii -i across a direct current sourceof potential having its positive terminal at 35 and its negativeterminal at 35. The control grid 7 25 is connected between the phctotube33 and the resistor at point When the phototube $3 is in darkness anegative potential is placed on the control grid 25 so that the tube 25will not If the tube 24 does not conduct, a positive potential is placedon the control gird ii and the tube M is placed in condition forconducting a current. When the phototube 3'3 receives light, a positivepotential is placed on the control grid 25 so that the tube 2 3 willconduct'and because of the load resistor 28, the control grid 57 isdriven negative and the tube M is placed in a condition so that it willnot conduct a current.

In the anode circuit l l is a relay coil 38 which actuates a relayswitch 39. The relay switch is shown in the open position which is thecondition when no current flows through tube it; The relay switch mayactuate a motor or any other suitable mechanism which is desired Theoperation of the device is as follows: When the-tube 33 is in darkness,thetube 21% will not conduct and a positive potential is placed on thegrid ll. This is the normal condition of the bias on the grid ii. Forany operation regardless'of no particular means for controlling the biason the grid ii, the grid ll'is'normally maintained positive and whetheror not the current will flow through the circuit from the point. [8' tothe point 39 depends on the bias of the control grid When the controlgird i3 is driven positive by tube it receiving sufficient light,currentwill flow from point it to point :9 and will continue to flowuntil the control grid i? is driven negative by the photocell 33receiving light regardless oi .the condition of light on tube it.

. necting a circuit employing a choke coil 38 and a resistor ll inparallel with the gas-filled tube it. It has been found that there is agradual tapering off of the amount of current that the tube it willconduct when a negative bias is placed i want it distinctly understoodthat the par- However, it is pnon the control grid ii and where it isdesired to,

immediatelystop the flow of current throfig lhfi function of alwaysconducting the current it is set for and in eflect what the choke coilill does isto take'all of the current from the positive terminal l8 andconduct it to ground when a negative potential is placed onthe grid 1?.This has the efiect of immediately stopping the flow of currentthrou'gh'tube l6 whereas otherwise there may be a small amount ofcurrent flow through tube 53 for a short time which is undesirable insome operations, The amount oi currentthat a choke coil to will alwaysconduct depends upon the point of adjustment of the adjustable resistorcontact 5-2. The choke coil Ml itself has no control on the. device butthe minute the grid l? is driven sufficiently negative that the chokecoil will conduct all of the current from point It to point it, the tubeill will cease to conduct. The choke coil therefore has the effect ofimmediatelystopping the flow of current through the tube ill when thecurrent through the tube M reaches a certain minimum. The choke coil hasmany advantages in operations where it is desired to immediately breakthe circuit sot-hat tube ill will not conduct.

The choke coil circuit embodyingthe choke coil til and the resistor 4 lis connected in parallel with the'tube H] by connecting the circuit frompoint 43' to the ground l9.

Figure 2 is similar toFigure 1. The only real difference is that thetube i4 is in the cathode circuit of the tube ill rather thaninthe anodecircuit. The operation of the device in Figure 2 is substantially thesame. The circuit employing the choke coil 40 and the resistor ll isconnected in parallel with the tube it by having it connected from thepoint 53 to the point :6. The vacuum tube l4 serves substantially thesame function whether it is connected in the anode circuit of the tubeill or connected in the cathode circuit of tube ill.

Throughout the specification and claims when ever I speak of a positiveor negative potential, or a positive or negative bias, I mean therelative potential or bias of the control grid in respect with itscathode; The cathode and grid may both be at a positive potential but ifthe grid more positive than the cathode, apositive bias or potential isplaced on' the grid. Likewise both may have a positive potential but ifthe grid is less positive than the: cathode, arelativeiy negativepotential is placedon the grid.

I claim as my invention: 1

1. An electronic circuit comprising'a source of direct current, a firstseries circuit connected to said source comprising a vacuum amplifyingtube and a gas-filled amplifying tube, each of said tubes having ananode circuit, a cathode circuit and a control grid, 2, second seriescircuit corn prising a choke coil and a resistor connected in parallelwith the gas-filled amplifying tube, the control grid of said vacuumtube being normally biased so as to enable the vacuum tube to conduct acurrent, independent vo1tage-applying means controlling the bias on thecontrol grid of the gas-filled tube thereby controlling the ionizationof the gas-filled tube and means for preventing or stopping the flow ofcurrent through the gasfille'd tube including voltage-applying means forplacing suflicierit negative bias on the control said third amplifyingtube such that the two tubes are 180 degrees out of phase, the controlgrid of said third amplifying tube normally biased so as to enable thevacuum tube to conduct a current, independent voltage-applying meanscontrolling the bias on the control grid of the gasfilled tube forcontrolling the ionization of the 6 gas-filled tube, and means forpreventing or stopping the flow of current through the gasfilled tubeincluding voltage-applying means placing sufficient positive bias on thecontrol grid of the third amplifying tube which renders the vacuum tubenon-conducting.

SAMUEL C. HURLEY, JR.

REFERENCES CITED The following references are of record in the his ofthis patent:

UNITED STATES PATENTS Number Name Date 2,124,848 Powell July 26, 19382,356,195 Balsley Aug. 22, 1944 2,404,754 Simpson July 23, 1946

